Defying traditional laws of physics, researchers may have
found a way to blast through imminent roadblocks on the highway
to faster and smaller computers.

Using modern quantum physics, a research team from NASA's
Jet Propulsion Laboratory (JPL), Pasadena, Calif., and the
University of Wales in the United Kingdom has discovered that
entangled pairs of light particles, called photons, can act as a
single unit, but perform with twice the efficiency.

Using a process called "entanglement," the research team
proposes that existing sources of laser light could be used to
produce smaller and faster computer chips than current technology
allows. Their paper appears in today's issue of the journal
Physical Review Letters.

"Our economy constantly depends on faster and faster
computers," said JPL researcher Dr. Jonathan Dowling, a co-author
of the paper. "This research potentially could enable us to
continue upgrading computers even after traditional manufacturing
procedures have been exhausted."

Currently, in a process known as optical lithography,
manufacturers use a stream of light particles to sculpt computer
chips. A chip is basically a grid of interconnected on-off
switches, called transistors, through which electric current
flows and enables computers to calculate. As companies crowd
millions of transistors into tinier chips, electric current
travels shorter distances, resulting in speedier processes.

Chipmakers shine a laser light onto photosensitive material
to create a stencil-like mask, which is used to carve silicon
into the components of transistors. However, the producers can
only provide transistors with dimensions as small as those of the
masks.

Today's state-of-the-art chips have transistors measuring
between 180 and 220 nanometers, approximately 400 times narrower
than the width of a human hair. While traditional computers have
the ability to perform with transistors as small as 25
nanometers, or 3,000 times narrower than a human hair, this
presents manufacturing obstacles.

The light manufacturers use to produce today's transistors
has a wavelength of 248 nanometers. It becomes increasingly
difficult to use light with shorter wavelengths to produce
transistors with smaller dimensions. In fact, according to a
central principle of optics called the "Rayleigh criterion," 248-
nanometer light can't create features smaller than 124
nanometers.

However, this new research, still in its theoretical stage,
could provide a bypass of the Rayleigh criterion. The research
team proposes that entanglement would allow the use of existing
sources of laser light of 248 nanometers to produce computer
chips with dimensions of a fourth of the wavelength (62
nanometers) or smaller compared to today's limits (124
nanometers).

Entanglement would allow researchers to use the intermingled
properties of two or more photons to obtain subwavelength spatial
resolutions. Albert Einstein called this intermingling of photons
process "spooky action at a distance" because the particles can
immediately influence each other over huge distances, even
halfway across the galaxy.

Here on Earth, entangled photons can be produced by passing
a light beam through a special crystal. In this quantum
lithography proposal, a pair of entangled photons enters a setup
with two paths. While the two particles travel together and act
as a single unit, it is impossible to determine which of the two
paths the pair has taken. In a strange effect of quantum
mechanics, however, each photon actually travels down both paths.

On each path, the photons act like a rippling wave with
peaks and valleys. After traveling on their own path for a while,
the two photons converge on a surface. Because the light
particles making up each wave were originally entangled, the
result of adding the photon waves together is to create patterns
on the surface equivalent to those made by a single photon with
half the wavelength.

This process, in essence, enables the entangled photon pair
to produce patterns twice as small on each side of a chip's
surface as can be created by the single photons in the
conventional optical lithography procedures. Entangling more than
two photons would improve results even further.

While a number of technical challenges remain, researchers
are already working on developing materials that would be
required for quantum lithography.

This research is part of the Revolutionary Computing
Technology project in the NASA/JPL Center for Integrated Space
Microsystems. The project is supported by the Deep Space Systems
Program in NASA's Office of Space Science. JPL is managed for
NASA by the California Institute of Technology in Pasadena.